Antifoam formulation

Abstract

Antifoam formulations contain a siloxane antifoam and a polyether/polysiloxane copolymer of the general formula (R 2 R*SiO) 2 (RR′SiO) x (R 2 SiO) y (RR″SiO) 2   (I) wherein R* is either R, R′, or R″, and wherein R′ is R 1 O—(CH 2 CH 2 O) a [CH 2 CH(CH 3 )O] b [CH 2 CH(CH 2 CH 3 )O] c —R 2 —  (R′) and wherein R″ is —R 2 —O—(CH 2 CH 2 O) d [CH 2 CH(CH 3 )O] e [CH 2 CH(CH 2 CH 3 )O] f —R 2 —  (R″) wherein R, R 1 , R 2 , a, b, c, d, e, f, x, y, and z are defined herein.

What is claimed is:  
     
       1. An antifoam formulation containing 
       (A) at least one antifoam based on siloxanes and  
       (B) 0.1 to 40% by weight of a polyether/polysiloxane copolymer of the formula  
       
         
           (R 2 R*SiO) 2 (RR′SiO) x (R 2 SiO) y (RR″SiO) z   (I)  
         
       
       in which R, independently of one another, denote identical or different, optionally substituted hydrocarbon radicals having 1 to 30 carbon atoms, R* denotes either R, R′ or R″; wherein R′ and R″ are: 
       
         
           R 1 O—(CH 2 CH 2 O) a [CH 2 CH(CH 3 )O] b [CH 2 CH(CH 2 CH 3 )O] c —R 2 —  (R′) or  
         
       
       
         
           —R 2 O—(CH 2 CH 2 O) d [CH 2 CH(CH 3 )O] e [CH 2 CH(CH 2 CH 3 )O] f —R 2 —  (R″)  
         
       
       where R 1  denotes either hydrogen, an alkyl, aralkyl, aryl or R—C(O) radical, x is on average 0.1 to 200, y is 1 to 1000, z is on average 0.01 to 2.0, and a, b, c, d, e and f have values between 0 and 1000, with the proviso that the sum (a+b+c) and the sum (d+e+f) each have a value of 2 to 2000, R 2  denotes an alkylene radical having 2 to 10 carbon atoms, 
       R″ is the divalent linking group in common with a group RR″SiO, or when R* is R″, the group R 2 R″SiO in a first polyether/polysiloxane copolymer of the formula (I) and with a group RR″SiO or R 2 R″SiO in a second polyether/polysiloxane copolymer of the formula (I) such that said first and second polyether/polysiloxane copolymers (I) are linked together by an R″ bridging unit, the antifoam based on siloxanes (A) and the polyether/polysiloxane copolymer (B) being different.  
     
     
       2. The antifoam formulation of  claim 1 , wherein a and b are between 5 and 50; c, d, and f are 0, e is from 20 to 150, x is from 1 to 10, y is from 3 to 100, and z is from 0.5 to 1.5. 
     
     
       3. The antifoam formulation of  claim 1 , wherein the polyether/polysiloxane copolymer of the formula (I) has a cloud point of less than 15° C. 
     
     
       4. The antifoam formulation of  claim 1 , comprising 
       (A) 1 to 90% by weight of antifoam based on siloxanes,  
       (B) 0.1 to 20% by weight of a polyether/polysiloxane copolymer of the formula (I),  
       (C) 0 to 20% by weight of emulsifiers and  
       (D) water, and optionally preservatives, thickeners and further additives.  
     
     
       5. The antifoam formulation as claimed in  claim 4 , wherein 2 to 20% by weight of emulsifiers are present. 
     
     
       6. The antifoam formulation as claimed in  claim 4 , wherein at least one emulsifier is selected from the group consisting of sorbitan fatty esters, ethoxylated sorbitan fatty esters, ethoxylated fatty acids, ethoxylated linear alcohols having 10 to 20 carbon atoms, ethoxylated branched alcohols having 10 to 20 carbon atoms, and glyceryl esters. 
     
     
       7. The antifoam formulation of  claim 1 , wherein said at least one antifoam based on siloxanes comprises a mixture of silica and a polyorganosiloxane. 
     
     
       8. In the process of pulp production where an antifoam is added to defoam aqueous media, the improvement comprising adding to said aqueous media the antifoam formulation of  claim 1 . 
     
     
       9. In the process of pulp production where an antifoam is added to defoam aqueous media, the improvement comprising adding to said aqueous media the antifoam formulation of  claim 2 . 
     
     
       10. In the process of pulp production where an antifoam is added to defoam aqueous media, the improvement comprising adding to said aqueous media the antifoam formulation of  claim 3 . 
     
     
       11. In the process pulp production where an antifoam is added to defoam aqueous media, the improvement comprising adding to said aqueous media the antifoam formulation of  claim 4 . 
     
     
       12. In the process of pulp production where an antifoam is added to defoam aqueous media, the improvement comprising adding to said aqueous media the antifoam formulation of  claim 6 . 
     
     
       13. An antifoam formulation containing 
       (A) at least one antifoam based on siloxanes and  
       (B) 0.1 to 40% by weight of a polyether/polysiloxane copolymer of the formula  
       
         
           (R 2 R*SiO) 2 (RR′SiO) x (R 2 SiO) y (RR″SiO) z   (I)  
         
       
        in which R, independently of one another, denote identical or different, optionally substituted hydrocarbon radicals having 1 to 30 carbon atoms, R* denotes either R, R′ or R″; wherein R′ and R″ are:  
       
         
           R 1 O—(CH 2 CH 2 O) a [CH 2 CH(CH 3 )O] b [CH 2 CH(CH 2 CH 3 )O] c —R 2 —  (R′) or  
         
       
       
         
           —R 2 O—(CH 2 CH 2 O) d [CH 2 CH(CH 3 )O] e [CH 2 CH(CH 2 CH 3 )O] f —R 2 —  (R″)  
         
       
        where R 1  denotes either hydrogen, an alkyl, aralkyl, aryl or R—C(O) radical, x is on average 0.1 to 200, y is 1 to 1000, z is on average 0.01 to 2.0, and a, b, c, d, e and f have values between 0 and 1000, with the proviso that the sum (a+b+c) and the sum (d+e+f) each have a value of 2 to 2000, R 2  denotes an alkylene radical having 2 to 10 carbon atoms,  
       R″ is the divalent linking group in common with a group RR″SiO, or when R* is R″, the group R 2 R″SiO in a first polyether/polysiloxane copolymer of the formula (I) and with a group RR″SiO or R 2 R″SiO in a second polyether/polysiloxane copolymer of the formula (I) such that said first and second polyether/polysiloxane copolymers (I) are linked together by an R″ bridging unit, the antifoam based on siloxanes (A) and the polyether/polysiloxane copolymer (B) being different,  
       wherein said at least one antifoam based on siloxanes comprises a mixture of  
       (aa) 1 to 15% by weight of at least one precipitated silica rendered hydrophobic in situ and having a BET surface area greater than 50 g/m 2 , a pyrogenic silica rendered hydrophobic in situ and having a BET surface area greater than 50 g/m 2 , and/or a pretreated, hydrophobic precipitated and/or pyrogenic silica having a BET surface area greater than 50 g/m 2 ,  
       (ab) 20 to 99% by weight of one or more polyorganosiloxanes of the formula  
       
         
           R 3   m (R 4 O) n SiO (4-n-m)/2   (II)  
         
       
       in which R 3  independently is an identical or different, optionally substituted, saturated or unsaturated hydrocarbon radical having 1 to 30 carbon atoms, and R 4  independently is hydrogen or an optionally substituted, saturated or unsaturated hydrocarbon radical having 1 to 30 carbon atoms, n has an average value of less than 0.5 and the sum (n+m) has a value from 1.8 to 2.4, 
       (ac) 0 to 10% by weight of a silicone resin comprising units of the formula R 3 SiO 1/2  and SiO 4/2 , and  
       (ad) 0 to 80% by weight of at least one organic compound having a boiling point greater than 100° C., selected from the group consisting of mineral oils, natural oils, isoparaffins, polyisobutylenes, residues from the oxoalcohol synthesis, esters of low molecular weight synthetic carboxylic acids, ethers of low molecular weight alcohols, phthalates, and esters of phosphoric acid.  
     
     
       14. The antifoam formulation of  claim 13 , wherein the antifoam based on siloxanes contains at least one polyorganosiloxane of the formula (II), in which R 3  denotes a methyl radical and R 4  denotes a linear or branched hydrocarbon radical having at least 6 carbon atoms, n is from 0.005 to less than 0.5 and the sum (n+m) is from 1.9 to 2.1. 
     
     
       15. In the process of pulp production where an antifoam is added to defoam aqueous media, the improvement comprising adding to said aqueous media the antifoam formulation of  claim 13 . 
     
     
       16. In the process of pulp production where an antifoam is added to defoam aqueous media, the improvement comprising adding to said aqueous media the antifoam formulation of  claim 14 .